1. Technical Field
The present invention relates to an oil feeding arrangement for a shaft seal and a bearing.
2. Background Art
A supercharger is known as a means for raising a drive power (horsepower) of a vehicle engine. The supercharger supercharges an air to the engine using a rotational force of the engine.
FIG. 3 of the accompanying drawings illustrates part of a conventional supercharger. In this illustration, a rotary shaft 3 extends in a shaft opening 2 of a casing 1 and is rotatably supported in the casing 1 by bearings 4 and 5 at its part close to one end thereof and by bearings 8 and 9 via a boss 6 and a shock absorption member 7 at the other end. A dumper pulley 10 is fixed on the boss 6 and the absorption member 7 along their periphery. The dumper pulley 10 is connected with an engine (not shown) by means of a belt 11 indicated by a single dot line and is driven by the engine. The absorption member 7 softens or absorbs an impact force from the engine when a power is transmitted to the shaft 3 from the engine via the belt 11 and the pulley 10. The absorption member 7 may be a rubber disc.
At the rightmost and of the shaft 3, mounted is a step-up or speed-up wheel 12. The wheel 12 has a gear 12a along its periphery. The gear 12a engages with another gear 13a mounted on one end of a shaft 13 of an F rotor (not shown). The shaft 13 extends in parallel to the shaft 3. The shaft 13 is rotatably supported in a bore 16 of the casing 1 via bearings 14 and 15. The shaft 13 is provided with an F timing gear 17 which engages with an M tinning gear 19 fixed at one end of a third shaft 18 of an M rotor (not shown). The shaft 19 is coaxial with the shaft 3 and parallel to the shaft 13. The shaft 18 is rotatably supported in another bore 20 of the casing 1 by bearings 21 and 22.
As the engine rotates, the shaft 3 of the supercharger is driven by the power from the engine transmitted via the belt 11 and the dumper pulley 10, and rotation of the shaft 3 is transmitted to the shafts 13 and 18 by way of the gears 12a, 13a and 19 so that the F rotor and the M rotor rotate respectively. Upon rotation of these rotors, an external air is sucked into the supercharger from an inlet elbow (not shown) and is fed or supercharged into the engine from an outlet elbow (not shown).
A shaft seal 23 is located between the shaft 3 and the shaft bore 2, and an oil chamber 24 is defined between the shaft seal 23 and the bearings 4 and 5. An oil feed hole 25 which substantially vertically extends in the casing 1 is formed to supply an oil to the oil chamber 24. Specifically, the oil is fed from an oil pump (not shown) to the hole 25, the bearings 5 and 4 and the oil chamber 24 in turn. An upper end of the oil feed hole 25 opens to the air in the highest portion of the casing 1. At the lower end of the oil feed hole 25, provided is a nozzle 24a for directing the oil to the bearings 5 and 4 and in turn to the oil chamber 24.
In the illustrated conventional supercharger, however, the oil fed from the feed hole 25 is introduced to the bearings 4 and 5 and soon discharged from an exit formed in the casing 2 below the shaft 13 (not shown). Therefore, when the shaft 3 changes its rotational speed, the oil in the oil chamber 24 changes its surface level. As a result, a certain part 23a of the shaft seal 23 which slidably contacts the shaft 3 is occasionally exposed. If the part 23a of the shaft seal 23 is not merged or soaked in the oil pool, the oil is not fed to an interface between the shaft 3 and the part 23a of the seal 23. This may result in excessive and rapid wearing of the bearings 4 and 5 and the seal 23 as well as seizing/burning of the same.